森林立地学会誌 森林立地42(1),2000,17〜21

Jpn.J.For.Environment42(1),17−21  2000

 

 

Growth and dry matter allocation of three tropical tree species seedlings under

different soil moisture conditions

 

 

Teresa-Namiko Nagashiro-Kanda

United Graduate School of Agricultural Sciences, Kagoshima University,

Kagoshima 890-0065

Toshio Nakao**, Satoshi Ito**, Masahiro Takagi**and Kangoro Nogami**

Faculty of Agriculture, Miyazaki University, Miyazaki 889-2192

 

   We investigated the responses of growth and dry matter partitioning of seedlings of Cedrela odorata (west Indian cedar), Swietenia macrophylla (Honduras mahogany) and Schizolobium parahybum (quamwood) to different soil water regimes: water deficit, wet and moderate. All species showed the maximum growths in height, diameter at root collar, leaf area, and total dry weight in the moderate condition. Relative growth rate (RGR) in the water deficit and the wet conditions for all species declined compared to those in the moderate condition. For S. macrophylla and S. parahybum, the degree of decline was greater in the water deficit condition. Decreases in the net assimilation rate (NAR) in the water dificit and the wet conditions were same level. Leaf area ratio (LAR) decreased in the water dificit condition for S. Macrophylla, and increased in the wet condition for S. parahybum. Thus, larger decline of dry matter allocation to leaves in the water deficit condition compared to those in the wet condition might relate to the severer dicline of RGRs. For C. odorata, the decline of RGR was severer in the wet condition in contrast to other two species. NAR slightly increased in the wet condition, and slightly decreased in the water deficit condition. LAR decreased in both wet and water deficit conditions, with a larger decline in the wet. The severe decline of RGR in the wet condition compared to those in the water deficit condition might result from the largely declined dry matter allocation to leaves.

 

  ナガシロ−カンダ テレサ−ナミコ・中尾登志雄・伊藤哲・高木正博・野上寛五郎:異なる土壌水分条件における熱帯産3樹種の実生稚樹の成長と物質分配

 南米アマゾンに自生する3種(Cedrela odorata, Swietenia macrophylla, Schizolobium parahybum)の造林適地を明らかにするために,これらの実生苗を用いて異なる土壌水分条件に対する成長および乾物分配様式の反応を調べた。土壌水分条件は過湿(−0.004MPa),乾燥(−0.80MPa〜−1.26MPa),適潤(−0.02MPa〜−0.06MPa)の3処理を設定した。3種ともに中庸な土壌水分処理で最大の苗高,地際直径,葉面積および乾燥重量を示した。S. macrophyllaおよびS. parahybumの相対成長速度(RGR)は,乾燥および過湿処理で適潤処理に比べて低下し,低下の割合は乾燥処理で大きかった。純同化速度(NAR)の低下の程度は乾燥及び過湿処理で同程度であった。葉面積率(LAR)はS. parahybumでは過湿処理で増加し,S. macrophyllaでは乾燥処理で減少しており,乾燥処理において葉への分配が過湿処理に比較して減少したことが,より大きなRGRの低下につながったと考えられる。C. odorataでも,適潤処理に比べて乾燥処理および過湿処理ではRGRが低下したが,その割合は過湿処理で大きかった。 NARは過湿処理で若干増加し,乾燥処理では若干低下していた。LARは乾燥処理および過湿処理の両方で低下したが,特に過湿処理での低下が大きかった。過湿処理で成長が低下したのは,光合成産物の葉への分配が減少したためと考えられた。


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